WL#1972 "Evaluate HAVING before SELECT select-list"

- Changed name resolution for GROUP BY so that derived columns do not shadow table columns
  from the FROM clause. As a result GROUP BY now is handled as a true ANSI extentsion.
- Issue a warning when HAVING is resolved into ambiguous columns, and prefer the columns from
  the GROUP BY clause over SELECT columns.


mysql-test/r/having.result:
  Correct result for updated GROUP BY name resolution.
sql/item.cc:
  - prefer GROUP columns, but if none is found use SELECT list
  - issue a waring when a field may be resolved ambiguously
  - more/fixed comments
sql/mysql_priv.h:
  More flexible find_field_in_tables().
sql/sp.cc:
  More flexible find_field_in_tables().
sql/sql_base.cc:
  More flexible find_field_in_tables().
sql/sql_help.cc:
  More flexible find_field_in_tables().
sql/sql_select.cc:
  - name resolution of GROUP/ORDER BY column references is differentiated:
    - GROUP BY is resolved in SELECT and FROM clauses
    - ORDER BY is resolved only in SELECT (as before)
  - more informative variable names
  - more comments

1 files changed, 6 insertions, 3 deletions

diff --git a/sql/mysql_priv.h b/sql/mysql_priv.h
index d8916149b77..8c27e0130a1 100644
--- a/sql/mysql_priv.h
+++ b/sql/mysql_priv.h
@@ -650,8 +650,13 @@ void execute_init_command(THD *thd, sys_var_str *init_command_var,
 			  rw_lock_t *var_mutex);
 extern const Field *not_found_field;
 extern const Field *view_ref_found;
+
+enum find_item_error_report_type {REPORT_ALL_ERRORS, REPORT_EXCEPT_NOT_FOUND,
+				  IGNORE_ERRORS, REPORT_EXCEPT_NON_UNIQUE,
+                                  IGNORE_EXCEPT_NON_UNIQUE};
 Field *find_field_in_tables(THD *thd, Item_ident *item, TABLE_LIST *tables,
-			    Item **ref, bool report_error,
+			    Item **ref,
+                            find_item_error_report_type report_error,
                             bool check_privileges);
 Field *
 find_field_in_table(THD *thd, TABLE_LIST *table_list,
@@ -765,8 +770,6 @@ TABLE *unlink_open_table(THD *thd,TABLE *list,TABLE *find);
 SQL_SELECT *make_select(TABLE *head, table_map const_tables,
 			table_map read_tables, COND *conds, int *error,
                         bool allow_null_cond= false);
-enum find_item_error_report_type {REPORT_ALL_ERRORS, REPORT_EXCEPT_NOT_FOUND,
-				  IGNORE_ERRORS};
 extern const Item **not_found_item;
 Item ** find_item_in_list(Item *item, List<Item> &items, uint *counter,
 			  find_item_error_report_type report_error);